Enhanced gene transfection efficiency by use of peptide vectors containing laminin receptor-targeting sequence YIGSR

Peptide-based non-viral gene delivery: A comprehensive review of the advances and challenges

Gene therapy is the most effective treatment option for diseases, but its effectiveness is affected by the choice and design of gene carriers. The genes themselves have to pass through multiple barriers in order to enter the cell and therefore require additional vectors to carry them inside the cell. In gene therapy, peptides have unique properties and potential as gene carriers, which can effectively deliver genes into specific cells or tissues, protect genes from degradation, improve gene transfection efficiency, and enhance gene targeting and biological responsiveness. This paper reviews the research progress of peptides and their derivatives in the field of gene delivery recently, describes the obstacles encountered by foreign materials to enter the interior of the cell, and introduces the following classes of functional peptides that can carry materials into the interior of the cell, and assist in transmembrane translocation of carriers, thus breaking through endosomal traps to enable successful entry of genetic materials into the nucleus of the cell. The paper also discusses the combined application of peptide vectors with other vectors to enhance its transfection ability, explores current challenges encountered by peptide vectors, and looks forward to future developments in the field.

Peptide Self-Assembly Facilitating DNA Transfection and the Application in Inhibiting Cancer Cells

Non-viral vectors have been developing in gene delivery due to their safety and low immunogenicity. But their transfection effect is usually very low, thus limiting the application. Hence, we designed eight peptides (compounds 1-8). We compared their performances; compound 8 had the best transfection efficacy and biocompatibility. The transfection effect was similar with that of PEI, a most-widely-employed commercial transfection reagent. Atomic force microscope (AFM) images showed that the compound could self-assemble and the self-assembled peptide might encapsulate DNA. Based on these results, we further analyzed the inhibitory result in cancer cells and found that compound 8 could partially fight against Hela cells. Therefore, the compound is promising to pave the way for the development of more effective and less toxic transfection vectors.

Multifunctional gene delivery vectors containing different liver-targeting fragments for specifically transfecting hepatocellular carcinoma (HCC) cells

Gene therapy is a promising strategy for HCC treatment, but it commonly faces the problem of low specificity in gene transfection. In this study, we designed and synthesized a series of peptide-based gene delivery vectors (H-01 to H-18) containing varied HCC cell-targeting fragments for specifically binding different receptors highly expressed on HCC cell membranes. The physicochemical properties of peptide vectors or peptide/DNA complexes were characterized, and the gene delivery abilities of peptide vectors were evaluated in HepG2 cell lines. The results showed that peptide vectors H-02 and H-09, which contained targeted fragments for ACE2 and c-Met receptors, respectively, could specifically transfect HCC cells in a highly -efficient manner in vitro. Furthermore, the liver-targeting function in vivo of Cy5.5 labeled H-02 (H-17) and H-09 (H-18) was investigated by fluorescence imaging.

Functional characterization of Labeo rohita muscle cell line for in vitro research

BACKGROUND

Labeo rohita represents the most dominant fish species in Indian aquaculture and the fish cell lines have been used as an excellent in vitro platform for performing various biological research.

METHODS AND RESULTS

The LRM cell culture developed from the muscle tissue of L. rohita was used to study the in vitro applications. The developed muscle cells were maintained in a Leibovitz's-15 (L-15) supplemented with 10% FBS (Fetal Bovine Serum) and 10 ng/ml bFGF at 28 ^oC temperature. The LRM cells showed fibroblastic-like morphology and was authenticated by sequencing mitochondrial gene 16S rRNA. The expression of myogenic regulatory factors (MRFs) was studied in different stages of LRM cells; however, the expression patterns varied at different passages. The MEF2A, Mrf-4, and Myogenin expressions were higher in passage 25, while the expression of MyoD was maximum in passage 15, and the expression of Myf-5 was highest in passage 1. The transfection efficiency of LRM cells revealed 14 % of the GFP expression with a pmaxGFP vector DNA. The LRM cells were susceptible to the extracellular products prepared from Aeromonas hydrophilla and Edwardsiella tarda. The acute cytotoxicity of six heavy metals (Hg, Cd, Zn, Cu, Pb, Ni) was assessed in LRM cells by a dose-dependent manner in comparison to IC₅₀ values obtained from MTT and NR assays. A revival rate of 70-75% was achieved when the LRM cells were cryopreserved at - 196 °C using liquid nitrogen.

CONCLUSION

The developed muscle cells serve as an functional in vitro tool for toxicological and biotechnological studies.

Transferrin receptor targeting segment T7 containing peptide gene delivery vectors for efficient transfection of brain tumor cells

Successful gene therapy for brain tumors are often limited by two important factors, the existence of blood brain barrier (BBB) and inefficient transfection of brain tumor cells. In this study, we designed a series of peptide-based gene delivery vectors decorated with T7 segment for binding the transferrin (Tf) receptors which were highly expressed on brain tumor cells, and evaluated their ability of gene delivery. The physicochemical properties of peptide vectors or peptide/DNA complexes were studied as well. The in vitro transfection efficiency was investigated in normal and glioma cell lines. Among these complexes, PT-02/DNA complexes showed the highest transfection efficiency in glioma cells and low cytotoxicity in normal cell lines, and it could transport DNA across the BBB model in vitro. Furthermore, PT-02/DNA could deliver pIRES2-EGFP into the brain site of zebrafish in vivo. The designed peptide vectors offered a promising way for glioma gene therapy.

Dual-modal polypeptide-containing contrast agents for magnetic resonance/fluorescence imaging

Dual-modal magnetic resonance/fluorescent imaging (MRI/FI) attracts moreandmoreattentions in diagnosis of tumors. A corresponding dual-modal imaging agent with sufficient tumor sensitivity and specificity should be matched to improve imaging quality. Tripeptide (RGD) and pentapeptide (YIGSR) were selected as the tumor-targeting groups and attached to gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) and rhodamine B (RhB), and then make two novel polypeptide-based derivatives (RGD-Gd-DTPA-RhB and YIGSR-Gd-DTPA-RhB), respectively. These derivatives were further characterized and their properties, such as cell uptake, cell cytotoxicity, MRI and FI assay, were measured. YIGSR-Gd-DTPA-RhB and RGD-Gd-DTPA-RhB had high relaxivity, good tumor-targeting property, low cell cytotoxicity and good red FI in B16F10 melanoma cells. Moreover, YIGSR-Gd-DTPA-RhB and RGD-Gd-DTPA-RhB possessed high uptake to B16F10 melanoma, and then achieve highly enhanced FI and MRI of tumors in mice for a prolonged time. Therefore, YIGSR-Gd-DTPA-RhB and RGD-Gd-DTPA-RhB can be applied as the potential agents for tumor targeted MRI/FI in vivo.

Acylation of antimicrobial peptide-plasmid DNA vectors formulation for efficient gene delivery in cancer therapy

Antimicrobial peptides/DNA complexes were designed based on AMPs chensinin-1b and its corresponding lipo-chensinin-1b conjugated with an aliphatic acid with different chain lengths and therapeutic genes. The main goal of such a complex includes two aspects: first, antimicrobial peptides deliver therapeutic genes to cancer cells and genes expressed in targeted tissue for cancer gene therapy, and, second, the antimicrobial peptide kills cancer cells when used alone as an anticancer agent. This study presents a model composed of chensinin-1b and its lipo-chensinin-1b and eGFP plasmids, which were used as reporter genes, and the final peptide/eGFP plasmid complexes were analyzed by TEM and DLS. The gene transfection efficiency of the complex was evaluated by a microplate reader, FACS and CLSM. Compared with Lipo2000, the antimicrobial peptide showed specific selectivity for transfection against cancer cells and mammalian cells. The peptides chensinin-1b and lipo-chensinin-1b binding with the eGFP plasmid displayed optimal transfection efficiencies at a mass ratio of 8. In addition, PA-C1b can deliver p53-eGFP plasmids into MCF-7 cancer cells, and the proliferation of cells was inhibited and even caused cell death. Overall, PA-C1b was screened and found to have the highest transfection efficiency for gene delivery and good cellular uptake capability. The in vivo transfection ability of PA-C1b was investigated using a tumor-bearing mouse model, and the transfection efficiency reflected by the fluorescence of expressed GFP was determined by in vivo imaging. Conclusively, the antimicrobial peptide PA-C1b could be used as the nonviral vector with high efficiency for cancer gene therapy.

Substance P containing peptide gene delivery vectors for specifically transfecting glioma cells mediated by a neurokinin-1 receptor

Gene therapy provides a promising treatment for glioblastoma multiforme, which mainly depends on two key aspects, crossing the blood brain barrier (BBB) effectively and transfecting target cells selectively. In this work, we reported a series of peptide-based vectors for transfecting glioma cells specifically consisting of several functional segments including a cell-penetrating peptide, targeting segment substance P (SP), an endosomal escape segment, a PEG linker and a stearyl moiety. The conformations and DNA-loading capacities of peptide vectors and the self-assembly behaviors of peptide/pGL3 complexes were characterized. The in vitro gene transfection was evaluated in U87, 293T-NK1R, and normal 293T cell lines. The transfection efficiency ratio of P-02 (SP-PEG₄-K(C₁₈)-(LLHH)₃-R₉) to Lipo2000 in the U87 cell line was about 36% higher than that in the 293T cell line. The neurokinin-1 receptor (NK1R) in U87 cells mediated the transfection process via interactions with the ligand SP in peptide vectors. The mechanism of NK1R mediated transfection was demonstrated by the use of gene-modified 293T cells expressing NK1R, as well as the gene transfection in the presence of free SP. Besides, P-02 could promote the pGL3 plasmids to cross the BBB model in vitro and achieved the EGFP gene transfection in the brain of zebrafish successfully. The designed peptide vectors, owing to their specific transfection capacity in glioma cells, provide a potential approach for glioblastoma multiforme gene therapy.

Development of A2G80 peptide-gene complex for targeted delivery to muscle cells

Therapeutic strategies based on antisense oligonucleotides and therapeutic genes are being extensively investigated for the treatment of hereditary muscle diseases and hold great promise. However, the cellular uptake of these polyanions to the muscle cells is inefficient. Therefore, it is necessary to develop more effective methods of gene delivery into the muscle tissue. The A2G80 peptide (VQLRNGFPYFSY) from the laminin α2 chain has high affinity for α-dystroglycan (α-DG) which is expressed on the membrane of muscle cells. In this study, we designed a peptide-modified A2G80 with oligoarginine and oligohistidine (A2G80-R9-H8), and prepared peptide/plasmid DNA (pDNA) complex, to develop an efficient gene delivery system for the muscle tissue. The peptide/pDNA complex showed α-DG-dependent cellular uptake of the A2G80 sequence and significantly improved gene transfection efficiency mediated by the oligohistidine sequence in C2C12 myoblast cells. Further, the peptide/pDNA complex promoted efficient and sustained gene expression in the Duchenne muscular dystrophy mouse models. The A2G80-R9-H8 peptide has the potential for use as a specific carrier for targeting muscle in gene therapy in muscular dystrophy.

The rational design of cell-penetrating peptides for application in delivery systems

Cell penetrating peptides (CPPs) play a crucial role in the transportation of bioactive molecules. Although CPPs have been used widely in various delivery systems, further applications of CPPs are hampered by several drawbacks, such as high toxicity, low delivery efficiency, proteolytic instability and poor specificity. To design CPPs with great cell-penetrating ability, physicochemical properties and safety, researchers have tried to develop new methods to overcome the defects of CPPs. Briefly, (1) the side chain of arginine containing the guanidinium group is essential for the facilitation of cellular uptake; (2) the hydrophobic counterion complex around the guanidinium-rich backbone can "coat" the highly cationic structure with lipophilic moieties and act as an activator; (3) the conformation-constrained strategy was pursued to shield the peptide, thereby impeding access of the proteolytic enzyme; (4) targeting strategies can increase cell-type specificity of CPPs. In this review, the above four aspects were discussed in detail.

Nucleic acid delivery to differentiated retinal pigment epithelial cells using cell-penetrating peptide as a carrier

Nucleic acid delivery to the eye is a promising treatment strategy for many retinal disorders. In this manuscript, retinal gene delivery with non-coated and chondroitin sulphate (CS) coated amphipathic and cationic peptides was tested. The transfection and gene knockdown efficiencies were evaluated in different retinal pigment epithelial (RPE) cell models including both dividing and differentiated cells. In addition, the mobility of peptide-based gene delivery systems was examined in porcine vitreous by particle tracking analysis. The results indicate that amphipathic and cationic peptides are safe in vitro and are capable of high transgene expression and gene knockdown in dividing cells. We further demonstrate that incorporation of CS improves the efficiency of gene delivery of peptide-based systems. Most importantly, the transgene expression mediated by both non-coated and CS coated peptides was high in differentiated as well as in human primary RPE cells which are typically difficult to transfect. Coating of peptide-based gene delivery systems with CS improved diffusion in the vitreous and enhanced the stability of the polyplexes. The results indicate that a peptide-based system can be fine-tuned as a promising approach for retinal gene delivery.

Oral delivery of non-viral nucleic acid-based therapeutics - do we have the guts for this?

Gene therapy with RNA and pDNA-based drugs is limited by poor enzymatic stability and poor cellular permeation. The delivery of nucleic acids, in particular by the oral route, remains a major hurdle. This review will focus on the barriers to the oral delivery of nucleic acids and the strategies, in particular formulation strategies, which have been developed to overcome these barriers. Due to their very low oral bioavailability, the most obvious and most investigated biomedical applications for their oral delivery are related to the local treatment of inflammatory bowel diseases and colorectal cancers. Preclinical data but not yet clinical studies support the potential use of the oral route for the local delivery of formulated nucleic acid-based drugs.

Peptide-based gene delivery vectors

Gene therapy as a strategy for disease treatment requires safe and efficient gene delivery systems that encapsulate nucleic acids and deliver them to effective sites in the cell.

1988-2018: Thirty years of drug smuggling at the nano scale. Challenges and opportunities of cell-penetrating peptides in biomedical research

In 1988, two unrelated papers reported the discovery of peptide vectors with innate cell translocation properties, setting the ground for a new area of research that over the years has grown into considerable therapeutic potential. The vectors, named cell-penetrating peptides (CPPs), constitute a now large and diversified family, sharing the extraordinary ability to diffuse unaltered across cell membranes while ferrying diverse associated cargos. Such properties have made CPPs ideal tools for delivery of nucleic acids, proteins and other therapeutic/diagnostic molecules to cells and tissues via covalent conjugation or complexation. This year 2018 marks the 30^th anniversary of a peptide research landmark opening new perspectives in drug delivery. Given its vastness, exhaustive coverage of the main features and accomplishments in the CPP field is virtually impossible. Hence this manuscript, after saluting the above 30^th jubilee, focuses by necessity on the most recent contributions, providing a comprehensive list of recognized CPPs and their latest-reported applications over the last two years. In addition, it thoroughly reviews three areas of peptide vector research of particular interest to us, namely (i) efficient transport of low-bioavailability drugs into the brain; (ii) CPP-delivered disruptors of G protein-coupled receptor (GPCRs) heteromers related to several disorders, and (iii) CPP-mediated delivery of useful but poorly internalized drugs into parasites.

POSS-cored and peptide functionalized ternary gene delivery systems with enhanced endosomal escape ability for efficient intracellular delivery of plasmid DNA

Biocompatibility, stability and high efficiency profiles are critical points for promoting the practical applications of gene delivery systems. The incorporation of cell-penetrating peptides (CPPs), REDV, and a nuclear localization signal (NLS) peptide sequence has been considered to be a promising strategy for developing efficient gene carriers to transfect vascular endothelial cells (ECs). However, these integrated multifunctional peptide carriers are usually limited by their inefficient targeting function and weak endosomal escape ability. Aiming to develop more efficient gene carriers, the integrated multifunctional REDV-G-TAT-G-NLS-C sequence was conjugated to polyhedral oligomeric silsesquioxane (POSS) by heterobifunctional poly(ethylene glycol) in the current study. This star-shaped polymer carrier complexed with the pZNF580 plasmid to form gene complexes, and then the histidine-rich peptide of REDV-TAT-NLS-H₁₂ (TP-H12) was incorporated into their surface to obtain ternary gene delivery systems with enhanced endosomal escape ability. These ternary gene delivery systems exhibited low cytotoxicity towards ECs and possessed high REDV-mediated cellular uptake, excellent internalization efficiency, rapid endosomal escape and high nucleus translocation capacity. The endosomal escape of the ternary complexes was improved due to the pH buffering capacity of the histidine residue in TP-H12 and the optimized macropinocytosis internalization pathway. Moreover, these CPP-based ternary gene delivery systems have high gene delivery efficiency and could improve the migration of ECs as demonstrated by gene expression and transwell assay. These systems may serve as a promising candidate for gene delivery and transfection in ECs, which is advantageous for EC migration and endothelialization on the biomaterial surface.

The structure and configuration changes of multifunctional peptide vectors enhance gene delivery efficiency

We designed a series of peptide vectors that contain functional fragments with the goal of enhancing cellular internalization and gene transfection efficiency. The functional fragments included a cell-penetrating peptide (R₉), a cationic amphiphilic α-helical peptide [(LLKK)₃-H₆ or (LLHH)₃], a stearyl moiety, and cysteine residues. Vectors were also synthesized with D-type amino acids to improve their proteolytic stability. The conformations, particle sizes, and zeta potentials for complexes of these peptides with pGL3 plasmid DNA were characterized by circular dichroism and dynamic light scattering. In addition, cellular uptake of the peptide/DNA complexes and gene transfection efficiency were investigated with fluorescence-activated cell sorting and confocal laser-scanning microscopy. Greater transfection efficiency was achieved with the vectors containing the R₉ segment, and the efficiency was greater than Lipo2000. In addition, the D-type C₁₈-c(llkk)₃ch₆-r₉ had about 7 times and 5.5 times the transfection efficiency of Lipo2000 in 293T cells and NIH-3T3 cells at the N/P ratio of 6, respectively. Overall, the multifunctional peptide gene vectors containing the R₉ segment exhibited enhanced cellular internalization, a high gene transfection efficiency, and low cytotoxicity.

The R₉ containing peptide vectors can improve the gene transfection efficiency.